Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1994-02-14
1995-07-25
Powell, William
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
216 18, 216 20, 216 67, 174254, 174266, 428901, B44C 122, C23F 102, B32B 300
Patent
active
054360625
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to the field of manufacture of printed circuit boards and relates to a process for the production of a metal-clad laminate for use in circuit board manufacture, as well as to a roll-to-roll process for the production of circuit boards using metal-clad laminates.
BACKGROUND OF THE INVENTION
Since the early days of electrotechnics, printed circuit boards have been in the form of standard singlelayer or multilayer "printed" circuits formed from a combination of flat current parts (connections of the electronic circuit) and an insulating plate (the electrically insulating, mechanical support). The structuring of the circuit (layout) takes place by photochemical processes. Apart from surface-mounted devices or SMD technology, the circuit boards have passages, which are used on the one hand for the through-assembly (electrical contacting and mechanical fixing) of simple electronic components (such as resistors, capacitors, coils, etc.) and on the other hand are used to electrically connect current paths of different layers of a circuit board by means of plated-through holes.
However, the development of more complex circuits has taken place on the plane of integrated circuits (IC's), which comprise a plurality of electronic elements (transistors) on a common substrate and which are protected by a casing (chips). These chips have a very high density and ever-increasing compression with respect to circuits, which largely takes place through the miniaturization or reduction of the conductor thicknesses and the conductor spacings in the Si-substrate in a sub-.mu.m range. The casing dimension of such chips remains of the same order of magnitude as the aforementioned simple components, for easy handling reasons, while the dimensions of the circuit board and their holes or plated-through holes has remained largely unchanged. Thus, the miniaturization of circuits has mainly taken place by means of integrated circuits, which are independent, function-linked units, which can be easily inserted on circuit boards.
The structural dimensioning of the printed circuit boards has only incompletely participated in this miniaturization. There has indeed been a certain miniaturization of circuit boards with conventional technology, but this has occurred less through rigorous compression than by the greatest possible narrowing of the conductors.
However, significant advances have been prevented by the unavoidable plated-through holes, which have hitherto been subject to precision improvements, but not to miniaturization. The reason for this is that the circuit board plated-through holes have reached a structurally caused lower limit and cannot undergo further size reductions because, apart from the drill diameter limit, a considerable amount of space is taken up by the soldering pads and the prepared solder surfaces. However, it would be desirable to manufacture substrates (circuit boards) with a ten times greater density, but this is not possible with the gradual miniaturization of standard technology. Such a dimensioning jump leads to conflicts of aims.
Circuit boards, prepregs and conductor films are generally 0.1 to 1 or 2 mm thick and their hole diameter is necessarily 0.2 to 0.5 mm. Such dimensions are consequently 2 to 3 orders of magnitude (100 to 1000 times) above the corresponding dimensions of the conductor thicknesses and spacings in integrated circuits. There is a very significant dimensional variation between circuit boards and IC's.
The reason for the conventional and to some extent archaic construction of circuit boards is that it was not hitherto necessary to make significant innovations in circuit board technology with respect to a downward dimensioning. The presently conventional construction also has a technical basis. In order to be able to support components, the circuit boards must have a certain strength and it has not hitherto been possible to get away from this. Limits are placed on the mechanical drilling for the production of plated-through holes, e.g. with
REFERENCES:
patent: 3820994 (1974-06-01), Lindberg et al.
patent: 4118523 (1978-10-01), Bingham et al.
patent: 4668332 (1987-05-01), Ohnuki et al.
patent: 4830691 (1989-05-01), Kida et al.
patent: 5232548 (1993-08-01), Ehrenberg et al.
Patent Abstracts of Japan, vol. 13, No. 407 (E-818), 8 Sep. 1989 referring to Japanese patent publication 1,147,887 (Showa Electric Wire & Cable Company) of 9 Jun. 1989.
Patent Abstracts of Japan, vol. 13, No. 407 (E-818), 8 Sep. 1989 referring to Japanese patent publication 1,147,891 (Showa Electric Wire & Cable Company) of 9 Jun. 1989.
Martinelli Marco
Schmidt Walter
Dyconex Patente AG
Farley Walter C.
Powell William
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